ABSTRACT

Context New criteria for the diagnosis of type 2 diabetes
mellitus have recently been introduced that lowered the diagnostic
fasting plasma glucose (FPG) concentration from 7.8 to 7.0 mmol/L (140
to 126 mg/dL).

Objective To determine if individuals with diabetes diagnosed by
the new FPG concentration criterion would have excessive glycosylation
(elevated hemoglobin [HbA1c] levels).

Results Among subjects with normal FPG concentrations,
HbA1clevels in the NHANES III (and the MRG) data sets were
normal in 97.3% (96.2%), slightly elevated in 2.7% (3.6%), and high
in 0.1% (0.2%). Among individuals with impaired fasting glucose,
HbA1c concentrations were normal in 86.7% (81.4%),
slightly elevated in 13.1% (16.4%), and high in 0.2% (2.2%). Among
diabetic patients diagnosed by the new FPG criterion only,
HbA1c levels were normal in 60.9% (59.6%), slightly
elevated in 35.8% (32.8%), and high in 3.4% (7.6%). In diabetic
patients diagnosed by the former FPG criterion, HbA1c
levels were normal in 18.6% (16.7%), slightly elevated in 32.5%
(21.0%), and high in 48.9% (62.3%).

Conclusions About 60% of the new cohort of diabetic patients in
both data sets have normal HbA1c levels. We believe that
diabetes should not be diagnosed in those with FPG concentrations less
than 7.8 mmol/L (140 mg/dL) unless excessive glycosylation is evident.
Individuals without excessive glycosylation but with moderate
elevations of FPG concentrations (6.1-7.7 mmol/L [110-139 mg/dL])
should be diagnosed as having impaired fasting glucose and treated with
an appropriate diet and exercise. This diagnostic labeling achieves the
goal of early intervention without subjecting these persons to the
potentially negative insurance, employment, social, and psychological
consequences of a diagnosis of diabetes mellitus.

Figures

The third National Health and Nutrition Examination Survey (NHANES
III) data set had 2836 subjects and the Meta-Analysis Research Group
data set had 8917. To convert hemoglobin A1c from
percentage of total hemoglobin to proportion of total hemoglobin,
multiply by 0.01. See Table 1 for percentage of subjects in each strata
of fasting plasma glucose concentrations and "Methods" for
description of study population and for determination of upper limits
of normal of hemoglobin A1c levels.

Figure 2. Distribution of Hemoglobin A1c Levels in
Those Diagnosed as Having Diabetes Mellitus by New and Old
Criteria

Diagnosis based on fasting plasma glucose concentrations of 7.0 to
7.7 mmol/L (126-139 mg/dL) and 2-hour glucose concentrations of less
than 11.1 mmol/L (200 mg/dL) and by the old criteria (the cohort of
patients diagnosed as having diabetes mellitus by 2-hour glucose
concentrations of 11.1 mmol/L (200 mg/dL) or higher but with FPG
concentrations <7.0 mmol/L [126 mg/dL]). To convert hemoglobin
A1c from percentage of total hemoglobin to proportion of
total hemoglobin, multiply by 0.01.

Figure 3. Prevalence of Retinopathy in Pima Indians

To convert hemoglobin A1c from percentage of total
hemoglobin to proportion of total hemoglobin, multiply by 0.01. To
convert glucose from milligrams per deciliter to millimoles per liter,
multiply by 0.05551. Data adapted from McCance et
al.51

Figure 4. Prevalence of Retinopathy in Egyptians

To convert hemoglobin A1c from percentage of total
hemoglobin to proportion of total hemoglobin, multiply by 0.01. To
convert glucose from milligrams per deciliter to millimoles per liter,
multiply by 0.05551. Data adapted from Engelgau et
al.52

Figure 5. Prevalence of Retinopathy in the Third National
Health and Nutrition
Examination Survey

Taken from unpublished data on 40- to 74-year-old participants
(Katherine Flegal, PhD, written communication, July 1997). To convert
hemoglobin A1c from percentage of total hemoglobin to
proportion of total hemoglobin, multiply by 0.01. To convert glucose
from milligrams per deciliter to millimoles per liter, multiply by
0.05551.

Tables

References

Letters

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